Content providers increasingly rely on content delivery networks (CDNs) to distribute content requested by a geographically diverse clientele. Content delivery networks reduce delivery costs, improve performance and robustness, and enhance a quality of experience for end users by caching copies of content in numerous locations to reduce the distance between end users and a given copy of the content.
In general, a CDN includes a distribution system made up of content serving nodes, or “surrogates,” that cache copies of content and deliver the content in response to requests from end user devices. The distribution system also distributes content within the CDN, with content typically originating at an origin server and being distributed among the surrogates that are closer, both topologically and geographically, to a service provider edge and therefore to the end users. A request router of the CDN functions as a request reference point for the CDN to end user devices. An end user device sends a content request to the request router, which selects a capable surrogate to handle the content request and then redirects the end user device to the selected surrogate. The end user device reissues the content request directly to the selected surrogate, which delivers the requested content to the end user device.